Scattering Theory of Mesoscopic Detectors

TL;DR

This paper develops a scattering theory framework to analyze how mesoscopic conductors act as detectors for two-level quantum systems, focusing on relaxation, decoherence, and charge screening effects.

Contribution

It introduces a scattering matrix approach to quantify relaxation and decoherence rates, emphasizing charge screening in multi-channel conductors.

Findings

Charge screening significantly affects decoherence rates.

Scattering matrix elements can predict relaxation times.

Charge screening behavior varies with conductor channel number.

Abstract

We consider a two-level system coupled to a mesoscopic two-terminal conductor that acts as measuring device. As a convenient description of the conductor we introduce its scattering matrix. We show how its elements can be used to calculate the relaxation and decoherence rates of the two-level system. Special emphasis is laid on the charge screening in the conductor that becomes important in the many-channel limit. Finally we give some examples that illustrate charge screening in different limits.